1. Field of the Invention
The present invention relates to phosphinines and metal complexes thereof, the preparation of the phosphinines and their use as ligands in catalytic reactions.
2. Discussion of the Background
The reaction of olefinic compounds, carbon monoxide and hydrogen in the presence of a catalyst to form aldehydes having one more carbon atoms is known as hydroformylation (oxo process). As catalysts in these reactions, use is frequently made of compounds of transition metals of group VIII of the Periodic Table of the Elements, in particular rhodium and cobalt compounds. Hydroformylation using rhodium compounds generally offers the advantage of higher selectivity compared to the cobalt-catalyzed reaction and is thus usually more economical. The rhodium-catalyzed hydroformylation is usually carried out using complexes comprising rhodium and preferably trivalent phosphorus compounds as ligands. Known ligands are, for example, compounds from the classes of phosphines, phosphites and phosphonites. A good review of the hydroformylation of olefins may be found in B. Cornils, W. A. Herrmann, xe2x80x9cApplied Homogeneous Catalysis with Organometallic Compoundsxe2x80x9d, Vol. 1and2, VCH, Weinheim, New York, 1996.
Each catalyst system (cobalt or rhodium) has its specific advantages. Different catalyst systems are therefore used depending on the starting material and target product, as the following examples show. If rhodium and triphenylphosphine are employed, xcex1-olefins can be hydroformylated at relatively low pressures. An excess of triphenylphosphine is generally used as phosphorus-containing ligand, with a high ligandi/rhodium ratio being necessary to increase the selectivity of the reaction in favor of the commercially desired n-aldehyde product.
The patents U.S. Pat. Nos. 4,694,109 and 4,879,416 describe bisphosphine ligands and their use in the hydroformylation of olefins at low synthesis gas pressures. High activities and high n/i-selectivities are achieved using ligands of this type, especially,in the hydroformylation of propene. WO 95/30680 discloses bidentate phosphine ligands and their use in catalysis, including hydroformylation reactions. Ferrocene-bridged bisphosphines are described, for example, in the patents U.S. Pat. Nos. 4,169,861, 4,201,714 and 4,193,943 as ligands for hydroformylations. Our phosphines don""t have bridging metals.
The disadvantage of bidentate phosphine ligands is the relatively high cost of preparing them. It is therefore often not economically viable to use such systems in industrial processes.
Rhodium-monophosphite complexes are suitable catalysts for the hydroformylation of branched olefins having internal double bonds, but the selectivity to terminally hydroformylated compounds is low. EP 0 155 508 discloses the use of bisarylene-substituted monophosphites in the rhodium-catalyzed hydro-formylation of sterically hindered olefins, e.g. isobutene.
Rhodium-bisphosphite complexes catalyze the hydroformylation of linear olefins having terminal and internal double bonds forming predominantly terminally hydroformylated products, while branched olefins having internal double bonds are reacted to only a small extent. Coordination of these ligands to a transition metal center gives catalysts of increased activity, but the operating life of these catalyst systems is unsatisfactory, among other things because of the hydrolysis sensitivity of the phosphite ligands. The use of substituted bisaryl diols as starting materials for the phosphite ligands, as described in EP 0 214 622 or EP 0 472 071, has enabled considerable improvements to be achieved.
According to the literature, the rhodium complexes of these ligands are extremely active hydroformylation catalysts for xcex1-olefins. The patents U.S. Pat. Nos. 4,668,651, 4,748,261 and 4,885,401 describe polyphosphite ligands which allow xcex1-olefins and also 2-butene to be converted with high selectivity into the terminally hydroformylated products. Bidentate ligands of this type have also been used for the hydroformylation of butadiene (U.S. Pat. No. 5,312,996).
Although the phosphinines mentioned are very good complexing ligands for rhodium hydroformylation catalysts, it is desirable to improve their effectiveness and stability still further.
An object of the present invention is to provide phosphinine complexes and methods for preparing phosphinine complexes.
Another object of the invention is to provide metal complexes containing phosphinine ligands and methods for preparing metal complexes of phosphinine ligands.
A further object of the invention is to provide methods for catalytic hydroformylation using phosphinine metal complexes.